The invention relates to a divided flywheel having two coaxial flywheel weights or flywheel elements and a spring arrangement arranged between them, having an intermediate support coaxial with the flywheel elements, which is coupled propulsively to the respective flywheel elements through a separate spring set permitting a relative rotation between the intermediate support and the flywheel elements.
Divided flywheels can be arranged on internal combustion engines instead of conventional one-part flywheels, in order to isolate the transmission line and the engine vibrationally from each other.
Due to the type of construction described above, the spring arrangement gives the flywheel elements or flywheel weights comparatively great rotary mobility relative to each other, which is dictated by the sum of the possible spring strokes of the springs sets.
The great relative mobility of the flywheel elements or flywheel weights is desirable particularly when strong jolts occur in the transmission line, for example when a clutch arranged between the engine and the transmission line is engaged abruptly. A comparatively great rotary mobility of the flywheel elements or flywheel weights relative to each other is furthermore also desirable at lower engine speeds, at which speeds an internal combustion engine generally tends to generate shaking vibrations.
The design of the divided flywheel is made such that the flywheel always operates in its so-called hypercritical range under normal operating conditions, that is to say the vibrations occurring at the flywheel have a frequency above the resonance frequency. The resonance frequency can accordingly be generated virtually only when starting the engine or when the engine is stalled.
In previous divided flywheels of the type described above, the great relative mobility of the flywheel elements or flywheel weights, desirable per se, can possibly lead to disturbing effects. Thus, for example, at higher engine speeds, at which the flywheel weights or flywheel elements execute rotary vibrations relative to each other of only relatively small amplitudes, disturbing vibrations of the intermediate support can be generated. Furthermore, during reactions to load changes, undesirably strong vibrations can be generated between the flywheel weights or flywheel elements.
Lastly, the great relative mobility of the flywheel weights or flywheel elements is rather disadvantageous in the case of prolonged generation of the resonance frequency.
It is therefore an object of the present invention to produce a divided flywheel with decidedly improved operational behavior.
This object is achieved in a flywheel of the type described above, in that a first spring set comprises long-stroke helicoidal springs which extend along a circular arcuate helical axis with a center of curvature lying on the flywheel axis. This first spring set operates with friction as a function of centrifugal force by said springs being urged by the centrifugal force against bearing surfaces arranged on the intermediate support and on the one flywheel element and bracing the springs radially outwards relative to the flywheel axis. A stop spring device is provided which is operative in the case of major relative rotation, and/or a slip coupling is provided which exhibits play, to be arranged between the intermediate support and the one flywheel element. A second spring set is provided which couples the intermediate support and the other flywheel element or the other flywheel weight, and comprises of relatively short-stroke and hard springs which operate with no or little friction even for major centrifugal forces.
The long-stroke helicoidal springs of the first spring set permit comparatively great relative rotations between the flywheel elements or flywheel weights at low engine speeds, so that the vibrational isolation of transmission line and engine is ensured even when vibrations of greater amplitude occur. Extremely quiet running is then accordingly ensured even at low operating speeds.
At higher speeds, the long-stroke springs become increasingly harder, because the centrifugal forces which increase with increasing speed cause increasing friction between the long-stroke springs and the bearing surfaces. A desirable hardening of the flywheel is achieved by this means, that is to say, during load changes no vibrations with excessively great vibration amplitudes can be generated between the flywheel elements or flywheel weights. The vibrational isolation between engine and transmission line at higher speeds can be ensured solely by the short-stroke springs of the other spring set, since the higher-frequency vibrations which occur at higher speeds have only a small amplitude. The hardening of the long-stroke springs simultaneously prevents the intermediate support from being able to execute large-amplitude rotary vibrations relative to the flywheel elements or flywheel weights.
At extremely low speeds and/or in the resonance range, destructive vibrations are prevented by the slip coupling which exhibits play and/or by the stop spring device, which become operative in the case of major relative movements between the intermediate support and the one flywheel element or the one flywheel weight and operate in the sense of hardening the long-stroke springs.
As an advantageous development of certain preferred embodiments of the invention, the spring sets are arranged superposed radially relative to the flywheel axis, while the spring set with the long-stroke springs is preferably positioned radially externally.
The bearing surfaces for the long-stroke springs are preferably constructed on a flywheel element as a bed of U-shaped or circular cross-section, it being contemplated for the bed to be lined with an antifriction layer on the side which braces the springs radially outwards. The bed provides the springs with a real bracing, the antifriction layer counteracts any excessive increase in the friction in the case of major centrifugal forces.
The bed may also form an annular chamber filled with lubricant according to certain preferred embodiments. In this case, on the one hand, the lubricant contributes to reduced wear of the springs, and on the other hand the hydraulic resistance of the lubricant acts as a vibration damper.
Abutment elements mutually opposite in the axial direction of the flywheel may be arranged at the end faces of the bearing surfaces according to certain preferred embodiments, the distance between which elements is shorter than the diameter of the long-stroke springs, and which exhibit mutually opposite openings or ports tangential to the flywheel axis, in which further helicoidal springs serving as resilient stops are fastened in cage fashion. In this case, the intermediate support engages by prolongations movable between the abutment elements with play in the circumferential direction into the space between the long-stroke springs and the further springs. This arrangement is conveniently provided in such a way that the prolongations are arranged respectively at both ends of the long-stroke springs and have a distance between them in the circumferential direction which corresponds to the distance between the abutment elements. Accordingly, in the case of relative rotation between the one flywheel element or the one flywheel weight and the intermediate support, the long-stroke springs are respectively compressed between the abutment elements at one end of the springs and one of the prolongations of the intermediate support, while the prolongation at the one end of the springs lifts from the latter and cooperates with the stop spring device in the case of a major relative rotation between the one flywheel element or the one flywheel weight and the intermediate support.
As an advantageous structural development of certain preferred embodiments, the slip coupling which exhibits play, which is preferably additionally operative between the intermediate support and the one flywheel element, may be arranged in the region of the internal circumference of the intermediate support, it being contemplated for spring elements which urge friction elements or friction rings of the coupling together to serve simultaneously to maintain firmly a bearing shell, associated with the one flywheel element, of a bearing fastening the other flywheel element.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.